1. The Field of the Invention
This invention relates generally to the field of transfer equipment. More particularly this invention relates to an apparatus to move a body from a supporting structure onto a truck. This invention also relates to mechanisms for coupling trailers to vehicles. More particularly, the invention relates to draw bars for securing trailers to trucks.
2. The Background Art
In many instances cargo or equipment needs to be loaded onto trucks. These loads are generally very large and may require specialized equipment to aid in loading and unloading. Loads maybe containers, dump-truck bodies, mechanical equipment such as cranes or spreaders, or the like. A special problem exists where the transfer of a load onto a truck needs to take place away from industrial equipment such as cranes, fork-lifts, or other supporting equipment. In such cases the capability to transfer the load must be relocatable to the location of the vehicle.
In some situations an operator of a truck may maximize the amount of cargo hauled during a trip by carrying a load mounted on the truck as well as drawing a trailer carrying additional cargo. For example, a dump truck may tow a trailer having an additional dump truck body mounted thereto. In this manner the truck may carry more cargo to or from a work site in a single trip. In some locations local laws may limit the weight of the load a truck is allowed to carry, based on the number of axles and the spacing between axles. Thus a trailer allows a truck to carry more load than the law would normally permit the truck to carry directly.
Dump trucks have long made use of such functionality by towing “pup trailers” having their own dumping body. In some cases a pup trailer may have its own hydraulics to effect dumping of a load. A dump truck may also tow a transfer trailer that does not have dumping hydraulics. The body of the transfer trailer must therefore be transferred into the dumping body on the truck in order for the load to be dumped. An advantage of a transfer trailer is that a truck can transport a large load because of the extended wheel base of the truck and transfer trailer, and yet can still have good maneuverability at the dump-site because of the short wheelbase of the dump truck. In addition the transfer trailer is made inexpensive through the elimination of hydraulic dumping hardware or other complex systems.
Some transfer trailers have small roller wheels that are powered along a track by an air or even electrical motor mounted to a transfer body resting on the transfer trailer. In typical operation an operator will position the back of the truck adjacent the front of the transfer trailer. The operator then exit the truck and goes to a switch at the back of the transfer trailer. The operator will then activate a switch that powers the wheels to propel the transfer body into the truck body. In some cases the roller wheels may roll along rails on the transfer trailer. In some systems, the operator must continually apply force to the switch as the transfer body moves from the trailer frame into the truck body in order to load the transfer body. Accordingly, the operator is obliged to walk along with the transfer body as it is loaded into the truck.
Such a manner of operation has many inconveniences and disadvantages. First of all, the operator must exit the safety and controlling environment of the truck in order to effect the loading of the transfer trailer body. The unprotected operator is very close to a moving object weighing many tons during the process. In addition, the amount of force that can be transferred between the transfer body roller wheels and the transfer trailer is limited by the frictional forces that the roller wheel can exert on the rails.
The amount of energy available to effect the transfer is also limited by the amount of energy that can be stored on the transfer body as pressurized gas, a battery, or the like. Thus, the wheels may not be able to overcome the weight of the transfer body if the transfer trailer is inclined. Thus, it would be an advancement in the art to provide a transfer system powered by the truck, in order to provide more power and energy to effect transfer of the transfer body. It would be a further advancement in the art to provide a transfer system that could be operated from within the cab of a truck.
Once the transfer body is loaded onto the truck the operator is then required to again exit the truck and unlatch the tailgate of the transfer body so the load can be dumped. The operator then must enter the cab of the truck to operate the controls for the hydraulics to dump the contents of the transfer body. Disadvantages to this manner of operation include the fact that the driver must exit the truck to unlatch the tailgate. It may also pose a safety risk, inasmuch as the load maybe exerting a force on the tailgate such that when the latch is released the load may spill out creating potential for potential harm of the operator.
In some applications it maybe advantageous for the truck to be in motion when the latch is released, such as when the truck is being used to spread material. Thus, a further disadvantage of such a conventional system is that the transfer body cannot be used to spread material, since the tailgate cannot be unlatched while the truck is in motion. Thus it would be an advancement in the art to provide a transfer body having a tailgate latch operable from within the cab of a truck.
A transfer trailer may be secured to a truck by a draw bar. The draw bar typically has a fixed length such that the truck must be positioned at a precise distance from the trailer in order for the draw bar to connect to a hitch on the truck. To accomplish this an operator will typically turn off the engine and leave the truck with the brake disengaged, the transmission in reverse gear, and the clutch engaged. The operator will then walk to the back of the truck and push a button activating the starter motor of the truck, thereby causing the truck to move toward the drawbar. The operator is thereby enabled to position the truck with sufficient precision to connect the draw bar to the truck.
This manner of operation has the principle disadvantage that an operator must stand behind a truck weighing many tons and set it in motion without access to a brake. A further disadvantage is that it is not conveniently performed with trucks having automatic transmissions. Thus it would be an advancement in the art to provide a drawbar that is extensible, enabling an operator to position the truck with less precision relative to the trailer. The operator would then be able to safely engage the brake of the truck before walking behind the truck to connect the draw bar to the truck. The draw bar could then be extended to reach the hitch on the truck, compensating for imprecision in the position of the truck relative to the transfer trailer. Such an extensible draw bar would have applications for a variety of trailers, besides transfer trailers, that makes use of draw bars in order to connect to a towing vehicle.